1. Field of the Invention
The disclosures herein generally relate to a projection system, an image processing apparatus, and a calibration method.
2. Description of the Related Art
Recently, more and more attention has been paid to a multiple projection technique in which a plurality of projectors are arranged such that projection images from the projectors are overlapped in overlapped areas and a single and high-resolution image can be projected on a screen.
Japanese Patent No. 3908255 discloses an image projection system relating to the multiple projection technique above described. In the image projection system disclosed in Japanese Patent No. 3908255, when calibration is performed, a reference image having four or more characteristic points whose coordinate positions are already known is projected on a screen from respective projectors. Here, the reference image is a known image in which, for example, bright spots or crosses are arranged at constant intervals. Then, positions of the characteristic points on the reference image captured (imaged) by a digital camera are detected. Further, based on the detected positions of the four or more characteristic points of the respective projectors, projection images of the respective projectors are transformed, the overlapped area is detected and a blending process is performed. By projecting the transformed and the blending-processed images on the screen from the projectors such that the images are arranged so as to have the overlapped area, a single and high-resolution image can be projected.
In the related art projection system described above, conditions are assumed in which an image can be projected in a wide screen like a wall without especially taking care of a position of the projection image. On the other hand, there may be a case in which a projection image is desired to be projected to fit within a plane screen which is separated from a wall like a white board with legs for an exhibition event, advertisement or the like, or a projection image is desired to be projected to fit within a projected area of a dedicated screen, which is attached to a wall and which is not separated from the wall, having patterns such as marble stone.
However, in the above described related art, in order to fit the connected projection images within the projected area, manual adjustment is required in which a user operates a control computer while visually checking the projection status. Thus, in a case in which a place where the control computer is located is remote from a place where the screen is located, because the user cannot visually confirm the projection states, the user is required to perform the adjustment while monitoring the video having low resolution by using a Web camera or the like, or cooperation is required in which a plurality of persons contact each other. Thus, it is not sufficient in terms of convenience. When being used as permanent signage, it is inevitable that the projectors become misaligned due to passage of time and/or vibration even after arrangement has been adjusted once. As a result, a minute deviation may degrade image quality extremely. Thus, a technique for easily performing the readjustment is required.